Crystal amplifier device



0ct 28, 1952 Amo ,96

CRYSTAL AMPLIFIER DEVICE Filed July 24, 1948 INVENTOR. Salvatore E Amco BY Patentecl Oct. 28, 1952 ICE v CRYSTAL AMPLIFIER DEVICE Salvatore F. Amico, East Boston, Mass., assignor to Sylvania Electric Products Inc.,- Salem, Mass., i a corporation of Massachusetts Application July 24, 1948, Serial No. 40,562

This invention relates to semi-conductors such as crystals and particularly to such devices useful as amplifiers, oscillators and the like. p

An object of the invention is to provide an effective crystal unit having at least three contacts, one of which may act as a control electrode to enable the device to act as an amplifier or the like.

A feature of the invention is a pair of flat metal strips in transverse contact with the apex line of a wedge-like crystal.

Other objects, features and advantages of the invention will be apparent from the following specificaton and its accompanying drawings, in which:

Figure 1 is a longitudinal section through the axis of a device according to the invention, and Figure 2 is another longitudinal section of the same device, taken through the longitudinal axis in a plane perpendicular to that of Figure 1. In the figures two thin sheets of strips l, 2 of metal may be held together by cement, for example a plastic cement, so that the two metal strips I, 2 are insulated from this assembly by the insulating layer 3. This assembly I, 2, 3 is then cemented into the center of a plastic bead or cylinder 4, or the bead or cylinder 4 can be molded around the laminated structure l, '2, 3. If desired the laminated metal strips l, 2 may be bent into S-shaped form for proper resilience either before or after being cemented together as described. The spacing between the metal strips I, 2 may be varied from an extremely small Value up to 0.002 inch, and the dimensions of each metal strip I, 2 may be varied, for example, in width and thickness to give the proper spring stiffness. For example, the insulating layer 3 may be 0.001 inch and the metal strips I, 2 may be 0.003 inch thick, 0.066 inch Width and inch long, and may be for example of tungsten or another similar metal. An alloy of platinum with 13 per cent rhodium works very well.

The ends of the metal strips 5, 6 in contact with the crystal may be machined to a sharp edge as shown, somewhat like a chiselled edge, but of course much sharper or in some cases the edge may be applied by well known electrolytic means. The actual edges 1, 8 may be on the nearer side of the two metal strips as shown in order to have them as close together as possible. The insulating layer 3 ends a short distance before the edge. The included angle of each point may be for example 45. The edges 1, B and should be within 0.001 inch of each other measured along the longitudinal axis of 6 Claims. (Cl. 175-366) the metal strips in other words the two edges should be substantially in a plane perpendicular to the axis of the metal strips.

The plastic bead 4 is inserted into a metal cartridge 9 having a slightly smaller inside diameter than the outside diameters of the bead 4, the difference, for example being 0.001 inch. The bead is preferably inserted so that its top or outside surface ll is about of an inch from the end l2 of cartridge 9. A metal plug l3 carrying a piece of semi-conductor crystal !6 soldered thereto is inserted into the metal Cartridge 9 from its other end [4. The metal plug l 3 should have a slightly larger outside diameter, for example 0.001 inch larger diameter, than the inside diameter of the metal Cartridge 9, in order that the plug I'I may be inserted into a Cartridge 9 as a forced fit. The solder [5 attaches the semi-conductor crystal IE to the metal plug l3 and to the Wire pigtail connection I T.

The crystal IS may for example be of germanium having incorporated therein a small amount of tin, for example 0.1%, as an actuating impurity often called a donator or acceptor impurity. The crystal is formed to have a sharp apex edge [8, the top I 9 of the crystal being made wedge shape for that purpose with the sides 20 and 2| leaning on the apex line. The crystal [6 being placed so that said apex line |8 is substantially in the plane as the edges 'I and 8 of Wire strips l and 2 and perpendicular to the longitudinal axes of said wires. The edges 1, 8 are then perpendicular to the edge [8, and the contact on the germanium will therefore be a point contact. The included angle between the surfaces ZI and 20 of the germanium crystal |6 may be for example about The crystal is suitably polished and etched to give proper electrical characteristics, for example being polished with 4/0 emery paper and oil polish and chemically etched.

The plug l3 is advanced into the Cartridge 9 until contact is just made, as may be indicated in an ohmmeter, and subjected to alternating current pulses to about 25 volts with a current limiting resistor for example of about 10 ohms in series. The pulses should be very short. After this pulsing, the plug !3 may be pulshed very slightly forward so as to bend the spring to secure proper electrical characteristics in the forward current carrying direction. About five milliamperes at one volt direct current for each contact may be satisfactory, for example, although other pulsing may be used for other purposes.

Reference is hereby made to my copending application Serial No. 40,561, filed concurrently herewith and to application Serial No. 39,665, filed July 20, 1948, by Frederic Koury, these applications all being assigned to a common assignee. These applications all contain disciosure and ciaims for multiple sharp contacts engaging a semiconductor, the sharp contact elements being separated by insulation.

What I claim is:

1. A semiconductor unit comprising a wedgeshaped semiconductor crystal, and two metal strip Contacts, an insulating layer cementing said strips together and spacing themfrom contact with each other, said strips engaging said body suflicientiy close to each other to efiect interaction and engaging the edge of the wedge-shaped crystai perpendicularly to give substantially point Contacts.

2. The combination of claim 1, in which the insulating layer is ofless than 0.002 inch thickness* U v 3. The combination metal strips have sharp; edges beveied toward the ends of the strip nearest each other: i ,14. A semi-conductor-nnit comprising a bodyof semi-conductive material having an edge, a contact: of large area engaging said body; and two additional contacts havingsharp'edges mutually closeto each other'and transverse to the edge of the semi-conductive-body and in engagement therewith. i i

5.-*A semiconductor nnit incliding a body of of claim 2, in which the i semiconductive material having an edge, a contact. of large area engaging said body, a pair of resiliently contoured strips cemented together and thrust endwise against said edge, said strips being formed each with a sharp edge, and the edges of said strips extending close to each other and transverse to the edge of said body.

6. A semi-conductor devicecomprisng a block of semi-conducting material having an edge, two metallic electrode members extending substantialiy at right angles with and across said edge. each of said members consisting of a ribbon having a sharp portion Contacting said edge to provide a small-area contact with said block, and a further electrode providing a low-resistance contact with said block.

SALVATORE F. AMICO.

REFERENCES CITED The following references are of record in the file oithis patentt UNITED STAT S PATENTS Great' Britain Mar. 10,- 1948 

